Flow and heat transfer enhancement of nanofluids in microchannel with blocks and grooves

A code based on the lattice-Boltzmann method was programmed. At various Reynolds numbers, simulations of the Cu/water nanofluid flow structure and heat transfer performance in a two dimensional microchannel with blocks (Re=10-100) and grooves (Re=50-200) were conducted, and the factors affecting the flow and heat transfer were explored. The flow and heat transfer of nanofluids with nanoparticle volume concentration of 0.5%, 1.0%, 1.5% and 2.0 % were simulated, obtaining the velocity and temperature distributions to compare with the results of base fluid. Flow analysis showed that recirculation zones formed behind the blocks and in the grooves when nanofluids flowed in the microchannel, and the size of recirculation zone increased with the increase of Reynolds number and nanoparticle volume concentration. The core of the recirculation zone in the groove gradually moved to the right wall as Reynolds number increased at the same nanoparticle volume concentration, and the direction of the main flow was getting horizontal. Heat transfer results indicated that the addition of nanoparticles could promote fluid flow and energy transport, so that the thermal boundary layer thickness decreased and the heat transfer was enhanced. The heat transfer enhancement increased with the increase of Reynolds number and nanoparticle volume concentration. It was also shown that the heat transfer enhancement by increasing the Reynolds number was limited. The results could give a fundamental understanding for designing highly efficient heat exchangers.